How to Perform a Bobcat MT85 Track Replacement Safely and Easily?

A Bobcat MT85 runs a 250x72x45 rubber track - 250 mm wide, 72 mm pitch and 45 links - the same belt listed for the Bobcat 220, X220, 320 and X320. The replacement itself is a small-machine job: support the loader, release the track tension, walk the belt off, inspect the rollers and idler while they are accessible, fit the new belt and re-tension it. What separates an easy job from an expensive one is doing the two things small track loaders make easy to skip: confirming the size first, and checking the running gear while the belt is off.

Last updated: October 7, 2026

This guide covers how to confirm the size, when the belt is finished, what to prepare, the replacement sequence, the safety step that matters most, and the checks that stop the new belt inheriting the old one's problem. The range is in the rubber track collection and the wider method is in the rubber tracks guide.

Confirm the size before anything moves

Three numbers, read from the marking on the belt that is on the machine and confirmed against the manual or parts book for the serial number: width, pitch and link count. On the MT85 that reads 250x72x45. Pitch has to engage the drive sprocket exactly and cannot be adjusted; link count is the belt's length, and one link out means the belt will not tension correctly.

The same size runs across several machines in this family, which is useful when sourcing and dangerous when ordering from a listing that names only the model. Read the code, write it down, and ask the supplier to confirm it back before the belt ships.

When the belt is finished

The order is predictable. First the lugs round off and the loader starts spinning where it used to bite. Then cracks appear at the lug base or across the belt's face, and the belt starts losing tension between adjustments. A cord strand visible at a cut, or a bulge in the belt, is the end - that belt can part under load. On a small machine the practical trigger is usually the operator noticing grip rather than a measurement, which is why the same walk-round that checks the belt should check the rollers.

Preparation

Work on firm, level ground with the attachment lowered and the machine isolated. Support the loader on stands rather than on the bucket, so the undercarriage is unloaded and the track can be released safely, and chock it so it cannot roll. Clean the undercarriage before you start: packed material holds the belt off its seat and hides the wear you are looking for.

For tooling, plan on a high-pressure grease gun for the tensioner, a bar for walking the belt off, a brush or scraper, and gloves and eye protection. Have the replacement belt on site before starting, and if the machine is due for rollers or an idler, have those too - the access work on a small loader is the same whether you change one part or three.

The safety step that matters most

The tensioner is a grease-filled cylinder under pressure. When you open the relief valve, the grease leaves with force and can be hot if the machine has been working. Keep your face and hands out of the line of the valve outlet, catch the grease in a container rather than letting it spray across the site, and never put your weight behind a gun or a valve that is not behaving. On a machine supported on stands with the undercarriage unloaded this is a controlled operation; done in a hurry, it is the part of the job that hurts people.

The replacement sequence

Release the tension until the belt is slack enough to move. Walk the belt off the sprocket and the idler, using the bar to lift the edge over the flange rather than levering against the belt's face, and keep the old belt - the code on it is what confirms the replacement if a question arises later.

Check the running gear while it is accessible. On an MT85 that means every roller, the idler and the drive sprocket: turn each roller by hand, look for weeping seals and play on shafts, check the sprocket teeth for hooks and the idler face for a groove. A worn idler or a hooked sprocket wears a new belt from the inside out, so this is the check that decides whether the new belt lasts.

Fit the new belt over the sprocket and idler with the tread facing out and the lugs engaged, then work it onto the frame in the reverse of the way the old one came off. Confirm it is seated on every roller before tensioning anything.

Re-tension by pumping the grease cylinder slowly in small increments, measuring as you go, until the belt reaches the figure in the machine's manual at the point the manual specifies. Then run the loader briefly and re-check, because a new belt takes its initial stretch in the first hours of work. The full sequence on a compact Bobcat machine is set out in replacing tracks on a Bobcat machine.

The habits that keep the new belt on

Three habits decide whether the belt you just fitted runs its full life. Re-check the tension after the first few hours. A new belt takes its initial stretch early, and a setting that was right when it went on is often slightly loose by the end of the first day. Keep the undercarriage clean. Packed mud and clay hold the belt off its seat and carry grit into the roller seals, which is the failure that starts the whole cycle again. And drive it like a small tracked machine. Pivoting repeatedly on the same spot, spinning a track on rock and running long distances on asphalt all shorten a belt's life far more than any difference between two documented products.

It is also worth knowing what the next failure will look like. On an MT85 the order is usually rollers first, then the idler and sprocket, then the belt - because the belt is protected until the steel around it stops doing its job. Recording the hours at each change, and the condition of the steel at the same time, is what turns the next replacement from a diagnosis into an order.

FAQs

What size tracks does a Bobcat MT85 take?

250x72x45 - 250 mm wide, 72 mm pitch and 45 links - the same belt listed for the Bobcat 220, X220, 320 and X320. Confirm against the marking on your machine's belt and its parts book.

Can I replace MT85 tracks myself?

Yes. It is a small-machine job: support the loader, release the tensioner safely, walk the belt off, inspect the rollers, idler and sprocket, fit the new belt and re-tension it to the manual's figure.

How tight should the new tracks be?

At the figure in the machine's manual, measured at the point the manual names, with the machine on level ground and the undercarriage cleaned. Re-check after the first few hours of work.

What should I check while the track is off?

Every roller, the idler and the drive sprocket: play on shafts, weeping seals, a grooved running surface, hooks on the sprocket teeth. Those parts are cheaper to replace in this job than in a second one.

Why does the new track come loose after a few hours?

New belts take their initial stretch in the first hours, which is why the tension is re-checked after the machine has run. A belt that keeps losing tension beyond that points at the tensioner rather than the belt.